The proper treatment of numerous pulmonary disorders and in particular, the treatment of chronic bronchitis and pulmonary emphysema often requires that the afflicted patient receive external breathing assistance to improve alveolar ventilation and reduce ventilatory work. In such treatment, the use of intermittent positive pressure breathing (IPPB) equipment has proven effective and also provides an efficient delivery system for medications employed in treatment such as decongestants, mucolytics, and bronchodialators.
A typical present-day manual respiration system suitable for home or clinic use comprises a venturi tube in combination with a nebulizer. Compressed gas is fed through the throat of the venturi by means of a nozzle. Apertures in the venturi tube body in open communication with the atmosphere permit air to be entrained with the flow of compressed gas through the venturi tube in accordance with Bernoulli's principle. In typical operation, the combined flow of gas and entrained air exiting from the venturi at a slight positive pressure enters a nebulizer chamber for mixing with atomized medication prior to inhalation by the patient. A finger controlled by-pass vent, open to the atmosphere, which has a significantly larger flow capacity than the nozzle, is connected to the compressed gas line, and opening of the vent effectively stops flow through the nozzle, allowing the patient to exhale against negligible back pressure. The exhaled gases return through the venturi tube and pass into the room via the apertures in the venturi tube body.
With sources of constant pressure gas, it becomes apparent that the pressure to the patient's lungs remains constant during inhalation. However, as patients may be afflicted with various pulmonary disorders, the desired lung pressure may also vary for proper treatment. In view of this need, adjustable pressure IPPB ventilators have been designed, such as the one disclosed in U.S. Pat. No. 3,653,379, issued to Joseph G. Glenn. The aforementioned patent discloses a venturi tube having a slidable nozzle. By varying the nozzle position with respect to the venturi throat, changes in the downstream pressure are effected without need for regulation of the inlet pressure. While effective, such apparatus is relatively expensive to manufacture, and this additional cost is passed on to the patient, who may need no more than one lung pressure setting.
As most respirators are hand-held, it is necessary that the weight of the device be minimized Furthermore, the IPPB valves presently available are difficult to sterilize and create cross-contamination problems.
It is therefore an object of this invention to provide an IPPB valve which may be readily adapted for varying lung pressure requirements of the individual patient, be lightweight for the convenience of the user, and be sufficiently inexpensive to be used on a disposable basis.